Fuel injection device for an internal combustion engine

ABSTRACT

A fuel injection device for a pressure-ignited internal combustion engine having pumps in line, that is, in which each injection pump supplies fuel to one cylinder of the engine. There are in each piston and cylinder assembly of the injection pump, complementary means adapted to cooperate in at least one given angular position of, and in at least one part of the delivery stroke of, the piston so as to deduct a part of the fuel displaced in the course of said delivery stroke.

FUEL INJECTIoN DEVICE FOR AN INTERNAL COMBUSTION ENGINE Marcel Regneault, Paris; Maurice Le Creurer, Tavemy, both of France Automobiles Peugeot, Paris, France Aug. 26, 1970 Inventors:

Assignee:

Filed:

Appl. No.:

Foreign Application Priority Data Nov. 20, 1969 France ..6939888 US. Cl ..l23/32 G, 123/32 R, 123/1396, 123/139.2, 417/273, 417/275, 417/279 Int. Cl ..F02b 3/00, F02m 39/00 Field ofSearch ..123/32.6, 32.61, 139 R, 139.6, 123/139.2; 417/273, 275, 279, 283, 284, 242, 303, 428

References Cited UNITED STATES PATENTS Stockmeyer ..417/275 Q 10 i to 1 July 18, 1972 FOREIGN PATENTS OR APPLICATIONS I 725,585 3/1955 Great Britain ..123/32.6

' Primary Examiner-Laurence M. Goodridge Assistant Examiner-Ronald B. Cox Attorney-Burns, Doane, Swecker and Mathis [57] ABSTRACT displaced in the courseof said delivery stroke.

9 Claim, 17 Drawing figures Patented July 18, 1972 5 Sheets-Sheet l Patented July 18, 1972 3 Sheets-$heet 2 Patented July 18, 1972 3,677,256

3 Sheets-Sheet 5 FUEL INJECTION DEVICE FOR AN INTERNAL COMBUSTION ENGINE The present invention relates to fuel injection devices for pressure ignited internal combustion engines.

As is known there are essentially two types of injection pumps for such engines So called "distributor pumps whose delivery chamber feeds in succession the difierent cylinders of the engine consequently only one piston-cylinder assembly is provided for supplying fuel to several engine cylinders.

So called in line or series pumps, the piston-cylinder assemblies of which are arranged in a line in a common body, one assembly being provided for each engine cylinder.

It is also known that in such engines the injection laws are such that there is necessarily a certain time lag between the start of the fuel injection and the ignition of this fuel. In other words, a large amount of fuel is already in the cylinder of the engine when ignition occurs. A poorly controlled and rather brutal combustion results. One of the consequences of this phenomenon is a particularly noisy operation of these engines.

This has been overcome in certain types of distributor pumps by the provision of an auxiliary device which deducts or takes off, at the start of the delivery phase, a part of the fuel and subsequently restores the fuel to the delivery chamber of the pump. Such a device does in fact enable the injection law to be modified so as to reduce the amount of fuel admitted in the cylinder in the course of the initial phase of the injection so that the aforementioned drawback is avoided to a large extent. This device may be completed by neutralizing means which suppresses its action under certain conditions of operation of the engine in which the aforementioned phenomenon is less apparent and less objectionable. Such an arrangement including both a deducting device and neutralizing means is described in U.S. Pat. No. 3,456,629 and in U.S. application Ser. No. 801,961.

The object of the present invention is to provide means for achieving the same result in the case of an injection device having pumps in line.

An assembly in line or series having injection pumps comprises a cylinder in which is received a piston whose reciprocating motion is usually controlled by a cam. The chamber defined by the cylinder communicates, first, by way of at least one supply orifice, with a source such as a fuel feed pump and, secondly, with an injection pipe connected to an injector. As the stroke of the piston is constant, means are provided for regulating the amount of fuel injected for each delivery stroke in accordance with the load and speed of operation of the engine. These means may comprise a governor which adjusts, through a simple mechanism, the angular position of the piston. The latter has on its periphery a helical groove which determines the end of the injection when it faces the supply orifices. It will be understood that a modification of the orientation of the piston results in a modification of the total amount of fuel injected.

The invention provides a fuel injection device for a pressure-ignited internal combustion engine of the type having in line or series injection pumps, said device comprising in each piston-cylinder assembly of the pump complementary means adapted to cooperate in at least one given angular position and in at least one part of the delivery stroke of the piston so as to deduct a part of the fuel displaced in the course of said delivery stroke.

According to one embodiment of the invention, said complementary means comprise a cavity which is formed in the lateral wall of the piston and communicates with the delivery chamber of the pump and a constricted passage in the wall of the delivery chamber.

This improvement enables the fuel injection law to be substantially modified for given conditions of operation of the engine. Thus, when the piston is in an angular position in which the cavity formed in its lateral wall and the calibrated orifice are disposed in facing relation to each other, a part of the fuel delivery is deducted or taken off. However,in order to avoid decreasing the total amount of fuel supplied to the engine, which is determined in accordance with the load and speed of rotation of the engine by conventional means, the deduction of fuel is compensated by prolonging the duration of the injection. The engine thus receives the required amount of fuelbut the injection of this amount is efi'ected in accordance with a law which is such that the combustion is controlled under better conditions and is less brutal 50 that the engine is more flexible and silent in operation.

Further features and advantages of the invention will be apparent from the ensuing description with reference to the accompanying drawings.

In the drawings FIG. 1 is a diagrammatic sectionalview of a part of an injection device according to the invention FIG. 2 is a sectional view of the injection pump of this device taken along line 2-2 of FIG. 1

FIG. 3 is a perspective view of the piston of the pump shown in FIGS. 1 and 2 FIGS. 4a, 4b, 4c are three diagrams representing respectively a conventional injection law and two laws obtained in accordance with the invention FIGS. 5, 6, and 7 are views of a modification of the invention which correspond to FIGS. 1, 2, and 3 respectively FIG. 8 is a partial axial sectional view of a modification of the injection pump FIG. 9 is a side elevational view of the piston of the pump shown in FIG. 8

FIG. 10 is a diagram representing the injection law obtained with the device shown in FIGS. 8 and 9 FIGS. 11 and 12 are two views, corresponding respectively to those of FIGS. 8 and 9, of a modification of the invention FIG. 13 is a diagrammatic sectional view of another embodiment of the device according to the invention, and

FIGS. 14 and 15 are two partial sectional views of two other modifications of the injection pump.

The part of the invention device shown in FIG. 1 comprises an injection pump P and an injector I connected to the pump by an injection conduit c. The other component parts of this device necessary for a comprehension of the invention have not been shown.

The pump P has a body 1 in which is provided a chamber 2 connected to the outlet of a fuel supply pump (not shown). The pump I receives a cylinder 3 provided with a first orifice 4 having a relatively large section and a second orifice 5 which has a small or constricted section 5a constituting a jet, and a larger section 5b. In the upper part, as viewed in FIG. 1, the body 1 receives a bushing 6 defining a seat 6a for a valve 7 and a plug 8 which maintains the cylinder and bushing in position and aflords a support face for a spring 9 which biases the valve 7 against the seat 60. The plug 8 constitutes a connection for the injection conduit c.

The cylinder 3 receives a piston I0, shown in perspective in FIG. 3. A very small clearance is provided between the piston and the cylinder. The piston 10 has a head 10a in which is formed a cavity 10b defined by a ramp having a roughly helical profile. This cavity communicates with the upper face of the piston by way of a longitudinal recess 11 known as a stop recess. Formed in the lateral face of the head 10a of the piston is an additional cavity constituted, in the embodiment shown in FIGS. I to 3, by a recess 12 having a roughly constant depth and a height h which is adapted, as will be described hereinafter in detail, to cooperate with the jet 5. The cylinder 3 and the piston 10 define a delivery chamberl3.

In the known manner, the piston 10 is shifted by a camshaft through a pushrod. These members have not been shown in the drawing. The piston 10 can be shifted angularly by a rack 14 whose movement in translation is controlled by a governor. The latter is responsive to the load and the speed of operation of the engine. The resulting angular movement of the piston determines, owing to the effect of the profile of the ramp 10c, the part of the stroke of the piston during which the fuel is delivered to the injector.

The injection device just described operates in the following manner:

Let it be assumed first of all that the engine operates under such load and at such speed that the piston 10 occupies the angular position shown in the drawing, in which the recess 12 faces the jet a. These conditions of operation may correspond to an idling engine. In this case, at the start of each injection cycle, the fuel compressed in the chamber 13 as soon as the head a of the piston has closed or masked the supply orifice 4, is pumped from the chamber, on one hand, to the injector I by way of valve 7 and the conduit c and, on the other hand, to the supply chamber 2 by way of the jet 5a and the orifice 5b. During a part of the delivery stroke of the piston, the flow of fuel actually injected is therefore equal at each instant to the difference between the volume of fuel displaced by the piston and the fuel escape flow through the jet 5. The amount of fuel supplied to the engine per unit time is therefore reduced and this reduction continues so long as the delivery chamber 13 communicates with the jet 5, that is, so long as the recess 12 faces this jet. Thus, it will be understood that it is possible to determine the injection law with precision by suitably choosing the ratio between the height h of the recess 12 and the delivery stroke of the piston 10. This will be explained more clearly with reference to FIGS. 40 to 40 which represent, with respect to time, the amount of fuel injected under identical conditions of load and speed of the engine, first, in the case of a conventional injection pump (FIG. 4a) and, secondly, in the case of two improved pumps according to the invention (FIGS. 4b and 4c).

In the diagram shown in FIG. 4a, the segment ab 1 corresponds to the rising of the needle valve of the injector, the segment be to the normal injection and the segment cd to the return of the needle to its seat. The total duration of the injection corresponds to the length ad and the total amount of fuel injected corresponds to the cross-hatched area of the trapezium abcd; The diagram shown in FIG. 4b represents the injection law in the case where the height h of the recess 12 is less than the delivery stroke of the piston 10. The part 0,, b,, c,, corresponds to the reduced injection with a controlled escape of a part of the fuel through the jet 5. The segment c d corresponds to the closure of the jet and the segment d e to normal injection with a flow equal to that of the pump.

The flow of the pump has been completed by a dotted line in this graph and is represented by a the letters a b 'lf It will be observed that the total duration of the injection, represented by the length a,f,, exceeds that of a conventional pump (FIG. 4a) and that the total amount of fuel injected (represented by the cross-hatched area) is thesame in both cases. Thus the injection law has been modified in such manner that although the total amount of fuel supplied to the engine upon each injection is practically unchanged, the amount of fuel already in the cylinder of the engine at the moment of ignition of the mixture is much less. The combustion is therefore less brutal and better controlled and the operation of the engine is much less noisy.

As concerns the diagram shown in FIG. 4c, it corresponds to the case where the height h of the recess 12 is at least equal to the effective delivery stroke of the piston for a given selected angular position of the latter, so that the controlled escape-of the fuel through the jet 5 occurs throughout the period a d of the injection and the injected flow is at each instant equal to the difference between the flow of the pump (shownby the dotted line a b 'c 'd and the escape flow. The duration a,d is therefore longer than the corresponding duration a l, of the preceding case, so that the total amount of fuel injected is unchanged.

It has already been indicated that the aforementioned modification of the injection law only occurs for the angular position of the piston in which the recess 12 and the jet 5 are in coincidence. For other angular positions of the piston, that is, for the other conditions of speed and load, the recess and the jet are not in facing relation and the injection is effected normally. In other words, in this embodiment, the neutralization of the deducting means occurs automatically and results from the very nature of these means. This should be stressed, since the desired modification of the injection law under precise given conditions can thus be achieved very cheaply.

It will also be observed that the function performed by the stop recess 11 and the supply orifice 4 cannot be compared with the function of the recess 12 and the jet 5. Indeed, when the recess 1 l is brought into alignment with the orifice 4 when the engine is stopped, the pressure in the delivery chamber 13 is too weak to open the valve 7 and all the fuel displaced is discharged to the supply chamber 2. On the other hand, when the recess 12 and the jet 5 are in facing relation, owing to the small section of this jet, the pressure established in the chamber 13 is sufficient to open the valve 7 and result in the supply of fuel to the injector I.

The modification of the invention shown in FIGS. 5 to 7 differs from the embodiment just described only in respect of the shape of the cavity on the periphery of the head of the piston. The piston of this modification carries the reference numeral 15 and the cavity is constituted by a recess having a greater circumferential extent, the depth of the recess varying. The depth of the recess in the region of the jet 5 is maximum for the position of the piston corresponding to an idling engine or an engine under low load, and decreases progressively when the piston is shifted angularly in response to an increased engine speed or load and finally becomes nil after a given rotation of the piston.

The injection law resulting from this device is very close to that shown in FIGS. 4b and 40, except that the effect of the deducting means is eliminated or neutralized progressively when the piston is shifted angularly in the direction of arrow F (FIG. 6).

FIGS. 8 and 9 are detail views of another modification of the invention also concerning the construction of the piston of the injection pump. In this case, the cavity on the periphery of the piston 16 does not directly communicate with the delivery chamber 13. This cavity is formed by an oblong recess 16:: which is separated from the delivery chamber by a bearing portion 16b and the inner end of the recess is connected to the delivery chamber through two passages 16c, 16d which extend radially and axially respectively.

This arrangement afiords an injection law which differs from those described hereinbefore and is represented in FIG. 10. At the start of each injection cycle (for the conditions for which the angular position of the piston is that shown in FIG. 8), owing to the fact that the orifice 5 is closed by the bearing portion 16b, the piston starts to deliver fuel to the injector and the pressure established is sufficient to produce the injection. This corresponds to the part a b of the diagram shown in FIG. 10. At this moment, the recess 16a comes in front of the orifice 5, a part of the fuel is transferred to the supply chamber 2 and a pressure drop occurs in the injection circuit which is such that injection ceases. This phase corresponds to the part b c d of the diagram. Thereafter, the pressure rises at the moment when the orifice 5 is once more covered by the piston 16 and the main injection takes place, which corresponds to the part d e f g of the diagram. It can be seen that this arrangement results in a double injection, the device being so arranged that the amount of fuel deducted is sufiicient to produce a pressure drop in the injection conduit which is such as to momentarily close the injector.

The embodiment shown in FIGS. 11 and 12 differs from that just described only in that the recess 17a formed in the piston 17 has a circumferential extent exeeding that of the recess 16a of the preceding embodiment. This arrangement also results in a double injection similar to that represented in FIG. 10.

Another embodiment is shown in FIG. 13 which is more complex and in which the piston of the injection pump, designated by the reference numeral 18, may be identical to one of the previously described pistons 10, 15, 16, and 17. It is illustrated as being identical to the piston 10 andconsequently has a recess 18a which opens into the delivery chamber 13.

The supply orifice 4 and the deducting orifice 5 are on the whole unchanged. Attached to each pump assembly is a fuel deducting device D comprising a body- 19 which is screwthreadedly engaged in the body of the pump and has a cylindrical portion 20 engaged in a fiuidtight manner in a cavit y 21 in the cylinder 3. A sealing element 22 affords a seal between the cylindrical portion 20 and the cavity 21. The

body 19 is hollow and defines a seat 23a and a cavity 23b for a closing member constituted by a piston 24 biased by a spring 25. A screwthreaded connection 26 connects the device D of each pump assembly with a conduit 27 connected to a common device D It is assumed that the engine equipped with the device according to the invention has four cylinders. The conduit 27 is connected through a ball check-valve 28 to the supply chamber of the pump so as to ensure, between'each injection cycle, an equilibrium between the pressures of the supply chamber 2, the conduit 27 and the cylindrical cavities 23b so that any possible leakage is compensated.

In the illustrated embodiment, the device D is similar to one of the auxiliary fuel deducting devices described in the US. Pat. No. 3,456,629 completed by a closing member 29 constituted by a key or a rotary member, for example actuated by the acceleration lever of the engine. This closing member can be shifted by mechanical, hydraulic or electrical means as a function of at least one parameter of the operation of the engine. The device D will not be described in detail. It will merely be mentioned that it comprises a piston 30 movable in opposition to the action of a spring 31.

The assembly shown in FIG. 13 operates in the following manner:

For low loads and low speeds,'the recess 18a of the piston 18 faces the orifice 5, the closing member 29 of the device D is open, and the device is able to exert a modifying effect on the injection law of the pump in the following manner At the start of each injection cycle, as in the case of devices shown in FIGS. 1 and 5, the fuel discharged by the pump piston 18 from the chamber 13 is sent, on one hand, to the injector and, on the other hand, to the chamber 21 by way of the orifice 5 and causes both the opening of the injector and the shifting of the piston 24 off its seat 23a. The volume of fuel displaced by the movement of the piston 24 causes the piston 30 of the device D to move so that the device can modify the injection law ofthe pump.

At the end of the injection period, the helical ramp of the piston 18 opens or unmasks the supply orifice 4, results in a pressure relief in the chamber 13 and, under the effect of this relief, the injector and the valve, corresponding to the valve 7 shown in FIG. 1, close. As the piston 24 is no longer exposed to pressure, it returns to its conical seat under the action of the spring 25. The same is true of the piston 30 of the device D The fuel in the chamber 21 is returned to the chamber 13.

For high loads and high speeds of the engine, the injection is effected normally without being subjected to the effect of the flow modifying device. This effect is eliminated, in accordance with the load, by the shifting of the recess 18 with respect to the orifice 5 and, in accordance with the engine speed, by the closure of the closing member 29.

It will be understood that operation with the devices shown in FIGS. 1 and 5 can also be contemplated with the devices shown in FIGS. 8 and 11 so as to achieve, for example, an injection law such as that represented by the diagram shown in FIG. 10.

The injection device assembly shown in FIG. 13 can moreover be employed with the modifications shown in FIGS. 14 and 15, which will now be described.

In F IG. 14, the device D is replaced by a device D in which the fuel deducting chamber is a chamber 32 defined by an elastic bag 33. The amount of fuel deducted in the course of each injection is absorbed by the elastic deformation of the bag of this chamber under the effect of the injection pressure.

FIG. 15 shows a device D in which the fuel deducting chamber is a chamber 34 having a movable wall formed by a membrane 35 which is subjected to the pressure of a compressrble fluid on the srde opposed to the chamber 34. This fluid is disposed in a chamber 36 which communicates with the atmosphere by way of a ball check-valve 37.

As previously mentioned, the amount of fuel deducted upon each injection is absorbed by the increase in the volume in the chamber 34 as a result of the deformation of the membrane 35, the fluid in the chamber 36 being compressed.

The assembly described with reference to FIGS. 13 to 15 affords the possibility, among other advantages, of neutralizing the modifying effect by two different means namely, on one hand, as in the case of the other embodiments, upon rotation of the piston of the injection pump under the action of the governor, and. on the other hand, when the closing member 29 is shifted by the acceleration lever of the engine.

Having now described our invention what we claim as new and desire to secure by Letters Patent is 1. A fuel injection device for a pressure-ignited internal combustion engine having series injection pumps, that is, in which each injection pump supplies fuel to one cylinder of the engine, said device comprising, in each piston and cylinder assembly of the injection pump, complementary means adapted to cooperate in at least one given angular position of, and in at least one part of the delivery stroke of, the piston so as to define a discharge path for the fuel and deduct a part of the fuel displaced in the course of said delivery stroke, said device further comprising a first fuel deducting device having a varia- I ble capacity chamber defined by a piston for receiving said deducted fuel and a second fuel deducting device [said two fuel deducting devices being] connected in series relation with said first deducting device, and a closing member controlled in v accordance with a parameter of the operation of the engine such as the speed and/or the load of the engine to selectively allow and preclude communication between the two fuel deducting devices.

2. A device as claimed in claim 1, wherein said closing member is adapted to be shifted by the acceleration lever of the engine.

3. A device as claimed in claim 1, wherein said second fuel deducting device comprises a variable-capacity chamber defined by a piston biased by elastically yieldable means.

4. A device as claimed in claim 1 for an engine having a plurality of cylinders, wherein the second fuel deducting device and the closing member are in series with the fuel deducting devices corresponding to the respective cylinders of the engine. I

5. A device as claimed in claim 1, wherein the second fuel deducting device comprises a variable-capacity chamber defined by a membrane having a face which is opposed to said variable capacity chamber and subjected to the action of a compressible fluid.

6. A device as claimed in claim 1, wherein said means comprises a cavity in a lateral wall of the piston, communicating with a delivery chamber of the pump and a throttling orifice in the wall of the delivery chamber, opening in said variable capacity chamber, said cavity being a recess which opens directly into said delivery chamber.

7. A device as claimed in claim 1, wherein said means comprises a cavity in a lateral wall of the piston, communicating with a delivery chamber of the pump and a throttling orifice in the wall of the delivery chamber, opening in said variable capacity chamber, said cavity being a recess which is separated from said delivery chamber by a portion of said lateral wall of the piston, a conduit being formed in the piston between an inner end of said recess and said delivery chamber.

8. A device as claimed in claim 7, wherein said recess has a substantially constant depth.

9. A device as claimed in claim 7, wherein said recess has a depth which varies along the circumferential extend of the recess. 

1. A fuel injection device for a pressure-ignited internal combustion engine having series injection pumps, that is, in which each injection pump supplies fuel to one cylinder of the engine, said device comprising, in each piston and cylinder assembly of the injection pump, complementary means adapted to cooperate in at least one given angular position of, and in at least one part of the delivery stroke of, the piston so as to define a discharge path for the fuel and deduct a part of the fuel displaced in the course of said delivery stroke, said device further comprising a first fuel deducting device having a variable capacity chamber defined by a piston for receiving said deducted fuel and a second fuel deducting device (said two fuel deducting devices being) connected in series relation with said first deducting device, and a closing member controlled in accordance with a parameter of the operation of the engine such as the speed and/or the load of the engine to selectively allow and preclude communication between the two fuel deducting devices.
 2. A device as claimed in claim 1, wherein said closing member is adapted to be shifted by the acceleration lever of the engine.
 3. A device as claimed in claim 1, wherein said second fuel deducting device comprises a variable-capacity chamber defined by a piston biased by elastically yieldable means.
 4. A device as claimed in claim 1 for an engine having a plurality of cylinders, wherein the second fuel deducting device and the closing member are in series with the fuel deducting devices corresponding to the respective cylinders of the engine.
 5. A device as claimed in claim 1, wherein the second fuel deducting device comprises a variable-capacity chamber defined by a membrane having a face which is opposed to said variable capacity chamber and subjected to the action of a compressible fluid.
 6. A device as claimed in claim 1, wherein said means comprises a cavity in a lateral wall of the piston, communicating with a delivery chamber of the pump and a throttling orifice in the wall of the delivery chamber, opening in said variable capacity chamber, said cavity being a recess which opens directly into said delivery chamber.
 7. A device as claimed in claim 1, wherein said means comprises a cavity in a lateral wall of the piston, communicating with a delivery chamber of the pump and a throttling orifice in the wall of the delivery chamber, opening in said variable capacity chamber, said cavity being a recess which is separated from said delivery chamber by a portion of said lateral wall of the piston, a conduit being formed in the piston between an inner end of said recess and said delivery chamber.
 8. A device as claimed in claim 7, wherein said recess has a substantially constant depth.
 9. A device as claimed in claim 7, wherein said recess has a depth which varies along the circumferential extend of the recess. 